The relative comparison above is based on theoretical properties only. Practical compressor performance depends on actual volumetric and isentropic efficiencies. Figures 5 and 6 show actual relative capacity and EER respectively for a 3-ton scroll compressor at three A/C and two H/P Te/Tc conditions typically encountered in system performance rating tests compared to theoretical at same 20 ºF superheat and 15 ºF liquid subcooling.